Respiratory diseases, including lung cancer, are extremely important from the standpoint of epidemiology, since they are widespread and often fatal. The proposed research will attempt to provide information about the mono-oxygenase enzymes in lung which metabolize foreign compounds and certain physiological substrates. These lung enzymes have been suggested to be involved in the metabolism of foreign compounds like benzo(a)pyrene or benzidine. The method of approach will involve in vitro studies using whole lung microsomer isolated lung cells and whole lung perfusion. Isolated cells will be separated and characterized with regard to viability and function. Lung perfusion experiments will allow the evaluation of the metabolic function of the lung cell studies. Studies with whole lung microsomes will allow the screening of the lung mono-oxygenase activities which are most active and these activities will be evaluated with chemical inhibitors and inducers. The lung cell suspensions will be monitored using several of these substrates. Using these techniques, biochemical differences between characterized lung cell types can be established and used in the evaluation of the biochemical-pharmacological function of lung.